I am actually quite disappointed with sites/books which talk about circuit "schematics". They are all too basic. What i am looking for is a book which a) Will take a non-trivial schematic for an actual product and walk me through deciphering it b) Will show me a actual PCB and derive its schematic from it. This is kind of like trying to understand the architecture of a system given its codebase and documentation. While there are lots of books which walk you through understanding software (eg. Linux Kernel) i have not found one which will do the same for electronic schematics. As a person self studying Embedded/Electronics systems, i find this a big drawback for real-world understanding. Perhaps some experts here can chime in with suggestions on how i can acquire such a skill.
In all seriousness, the absolute crap that manifests from schematics developed in Eagle coming out of the open source community is a personal pet peeve. An example of almost everything you shouldn't be doing with respect to at least the following can be found here: color, symbology, scale, reference designators, typeface, labeling, orientation, functional grouping, density, overlap, flow, etc. It's a shame there's zero reference to industry standards like IEEE Std 315 and ASME Y14.44.<p>Abuse of color is probably the one thing that really drives me nuts. I'm of the opinion that if electrical intent cannot be cleanly and unambiguously conveyed in black and white, it's garbage.<p>I secretly wish EEs in general exercised the same level of meticulous attention to detail and pride that designers in the typeface community do, in the same vein as this comment[1].<p>[1] <a href="https://news.ycombinator.com/item?id=19608359" rel="nofollow">https://news.ycombinator.com/item?id=19608359</a>
Some hints on how to get to the meat of a circuit:<p>The most important thing is to learn what to ignore, stuff that has to be there to help a circuit work, but that don't tell you much about what it does<p>- ignore all the power stuff<p>- in particular capacitors oriented with the two lines horizontal are usually decoupling capacitors, ones oriented the other way tend to carry interesting signals<p>- learn to find and ignore the biasing resistors around transistors<p>Rules of thumb:<p>- outputs of transistors are usually inverted from their inputs if taken from the collector/drain<p>- signals usually move from left to right<p>- chips vaguely have inputs on the left and outputs on the right (or pins that work together grouped together)
I have more experience in reading analogue schematics, and I imagine this is less challenging in purely digital electronics, but to me understanding a schematic is really more about identifying the causal flow of information / signals, by recognising familiar patterns (amplifiers, filters, resonators, etc). This article is more an alphabet chart.
Too bad, the article only deals with how to recognize individual components (like a french dictionnary that would be entitled "how to read french").
One thing to be aware of: spark fun's schematics are generally flaming crap, along with most arduino stuff.<p>> Sometimes, to make schematics more legible, we'll give a net a name and label it, rather than routing a wire all over the schematic.<p>Net labels are the anti-readable-schematic. They're basically the electronics equivalent of GOTO. This is total bullshit.<p>People use net-labels when they don't want to bother spending time to make their schematic flow properly, or they're doing something dumb like drawing their schematic symbols with the pin-positions from the physical IC.<p>Good schematics should make the overall operation of the system easy to discern. You should have a consistent signal-flow (generally left-to-right, though the opposite also works). More complex systems should also use a hierarchical design with the interfaces between logical sections being clearly defined.
Probably already mentioned, but looking at the "schematic symbols" - I noticed they didn't mention the (usually international) form of values - ie 2k5 - meaning 2.5k.<p>Also - they show symbols for potentiometer and variable resistor, but they don't show how if you connect the wiper to one end of the potentiometer, that means "variable resistor" (and is how you usually make one - unless using the potentiometer as an actual rheostat, which means connecting between one end and the wiper, leaving the other end free; electrically it's equivalent to not leaving the wiper floating with respect to the other end, but in a real rheostat, there is no "other end" to connect with - not without modification of the rheostat).<p>Then the battery symbols - and this isn't on them, but more the "standard"; yes, positive is the long side for a series of cells - but on virtually every standard consumer battery cell (C, D, AA, AAA), which end is the positive end? Yep - the one with the "bump" or "short end".<p>Even on the 9 volt battery, the smaller terminal is the positive end.<p>The only time things are "proper" are with coin cells, where the positive end is the flat plate (usually with writing), with the negative being the smaller plate surrounded by the edge of the positive plate on the other side. Knowing humans, though, I wouldn't be surprised if there was a coin-style cell where that was reversed...<p>I expect, though I don't know, that the battery stuff is the result of history (much like how positive and negative aren't really correct per physics as to how current really "flows").<p>I'm sure there's more weird stuff in Sparkfun's tutorial; it seems mainly geared for an American audience, and also toward older-styled symbols (like you'd find on schematics from the 1960s-80s). Most of the newer style haven't changed too dramatically - but there are some differences (they did note the resistor differences - but I've seen some others).<p>I'll have to read this in more detail later...
The text shows US and international symbols for things like resistors. But when it comes to logic gates don't mention the IEC standard gate symbols. Like these:<p><a href="https://commons.wikimedia.org/wiki/Category:IEC_Logic_Gates" rel="nofollow">https://commons.wikimedia.org/wiki/Category:IEC_Logic_Gates</a>